/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.test.util;

import org.apache.flink.util.OperatingSystem;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

/**
 * ShellScript for creating shell script on linux and windows.
 */
public class ShellScript {

	public static ShellScriptBuilder createShellScriptBuilder() {
		if (OperatingSystem.isWindows()) {
			return new WindowsShellScriptBuilder();
		}
		return new UnixShellScriptBuilder();
	}

	public static String getScriptExtension() {
		return OperatingSystem.isWindows() ? ".cmd" : ".sh";
	}

	/**
	 * Builder to create shell script.
	 */
	public abstract static class ShellScriptBuilder {
		private static final String LINE_SEPARATOR = System.getProperty("line.separator");
		private final StringBuilder sb = new StringBuilder();

		void line(String... command) {
			for (String s : command) {
				sb.append(s);
			}
			sb.append(LINE_SEPARATOR);
		}

		public void write(File file) throws IOException {
			try (FileWriter fwrt = new FileWriter(file); PrintWriter out = new PrintWriter(fwrt)) {
				out.append(sb);
			}
			file.setExecutable(true, false);
		}

		public abstract void command(List<String> command);

		public abstract void env(String key, String value);
	}

	private static final class UnixShellScriptBuilder extends ShellScriptBuilder {

		UnixShellScriptBuilder(){
			line("#!/usr/bin/env bash");
			line();
		}

		public void command(List<String> command) {
			line("exec ", String.join(" ", command));
		}

		public void env(String key, String value) {
			line("export ", key, "=\"", value, "\"");
		}
	}

	private static final class WindowsShellScriptBuilder extends ShellScriptBuilder {

		WindowsShellScriptBuilder() {
			line("@setlocal");
			line();
		}

		public void command(List<String> command) {
			line("@call ", String.join(" ", command));
		}

		public void env(String key, String value) {
			line("@set ", key, "=", value);
		}
	}
}
